MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
MAY, 2003
(For general comments about the nature of these summaries, as well as
information on how to download the tabular cyclone track files, see
the Author's Note at the end of this summary.)
*************************************************************************
MAY HIGHLIGHTS
--> Damaging cyclone strikes eastern Madagascar
--> Bay of Bengal cyclone strikes Myanmar
--> Northwest Pacific active--tropical storm causes fatalities
in Philippines
--> First tropical storm of season in Northeast Pacific basin forms
*************************************************************************
***** Feature of the Month for May *****
UPDATED NORTHEAST PACIFIC STATISTICS
For the past two years I have featured tables of Atlantic and
Northeastern Pacific monthly net tropical activity (NTC). For this
month's feature I have included tables for the Northeast Pacific
basin--the Atlantic was featured in the March monthly summary. When
breaking up a tropical cyclone season temporally (into months), some
decisions have to be made regarding intermonthly cyclones. I have
previously explained in detail my reasoning here, and interested
persons can find this in the March, 2002, summary, which can be
obtained from any of the websites listed at the end of this summary.
Tropical cyclonic activity in the Northeast Pacific (NEP) during
2002 extended from late May into early November. The first table
below lists the monthly statistics for the months May through November,
inclusive, as well as the seasonal totals. The statistics cover the
entire NEP basin from the west coast of Mexico to the International
Dateline. The NSD, HD and IHD parameters do not include any days which
a system may have spent in the Northwest Pacific basin west of
longitude 180. The 2002 season in the NEP basin was about average--the
NTC was 97.
NOTE: The parameters NS, H, IH, NSD, HD, IHD and NTC are those which
are used by the Colorado State University forecast team headed by
Dr. Bill Gray. Documentation for these can found on the CSU website:
http://hurricane.atmos.colostate.edu/Forecasts/>
Northeast Pacific Tropical Cyclone Season of 2002
-------------------------------------------------
Month NS H IH NSD HD IHD NTC
MAY 1 1 1 5.50 2.75 0.50 10.09
JUN 1 0 0 2.00 0.00 0.00 1.47
JUL 3 2 1 14.75 6.25 2.25 21.09
AUG 5 3 3 16.00 6.75 2.50 33.29
SEP 2 0 0 10.75 3.50 2.00 10.02
OCT 3 2 1 13.25 4.25 1.75 18.78
NOV 0 0 0 2.50 2.50 0.00 1.86
TOTAL 15 8 6 64.75 26.00 9.00 96.60
The next table gives NEP statistics for the period 1971-2002,
arranged by months. The year 1971 was chosen as a starting point
since, even though the Dvorak method of satellite analysis had not
yet been introduced, there was extensive aerial reconnaissance of
NEP storms that season and during the following two. Reconnaissance
flights into NEP cyclones were curtailed after 1973, but by 1974 the
initial Dvorak method was being used and tropical cyclone intensities
in the Best Track file can be considered somewhat reliable.
Northeast Pacific Basin Monthly NTC Table
Based on Period 1971-2002
-----------------------------------------
Month NS H IH NSD HD IHD NTC
JAN 1 1 0 3.25 2.00 0.00 0.14
FEB 0 0 1 3.00 2.25 0.50 0.20
MAR 1 0 0 1.00 0.00 0.00 0.04
APR 0 0 0 0.00 0.00 0.00 0.00
MAY 16 9 2 55.25 16.75 2.75 2.06
JUN 68 36 14 251.25 93.25 26.00 10.59
JUL 120 65 36 526.25 234.75 74.25 23.45
AUG 127 77 37 659.25 265.50 60.50 25.08
SEP 113 69 35 548.50 263.25 79.00 24.23
OCT 64 37 20 301.25 137.00 40.75 13.13
NOV 11 3 0 33.50 8.25 0.00 0.89
DEC 2 1 0 7.50 1.00 0.00 0.19
TOTAL 523 298 145 2390.00 1024.00 283.75
AVG 16.3 9.3 4.5 74.7 32.0 8.9
The following chart tabulates the same set of NEP statistics but
arranged by year. The active period which abruptly began in 1982 and
continued through 1994, except for a short "coffee break" in the late
1980s, is most striking. Prior to 1982, the only really active year
was 1978, and following 1994, the only year with an above-normal NTC
was the strong El Nino year of 1997.
Northeast Pacific Basin Annual NTC Table
Based on Period 1971-2002
----------------------------------------
Year NS H IH NSD HD IHD NTC
1971 18 12 6 84.00 38.50 6.00 112
1972 14 8 4 83.25 33.75 4.50 88
1973 12 7 3 62.25 28.50 7.25 78
1974 18 11 3 63.75 22.25 2.50 79
1975 17 9 4 71.75 26.75 5.50 88
1976 15 9 5 66.50 27.25 9.75 97
1977 8 4 0 20.50 5.25 .00 22
1978 19 14 7 102.75 51.50 16.00 150
1979 10 6 4 33.75 13.75 3.25 56
1980 14 7 3 48.25 22.75 2.75 65
1981 15 8 1 58.00 18.25 1.00 57
1982 23 12 5 106.50 39.25 7.50 121
1983 21 12 8 110.00 47.75 16.25 152
1984 21 13 7 103.50 46.25 14.75 145
1985 23 13 8 108.50 49.75 8.50 142
1986 17 9 3 62.50 28.75 6.75 86
1987 20 10 4 78.50 29.00 7.75 100
1988 15 7 3 65.25 29.50 6.50 81
1989 17 9 4 67.25 27.25 5.75 88
1990 21 16 6 126.00 58.25 20.25 168
1991 14 10 5 86.25 44.00 14.00 119
1992 27 16 10 148.75 65.50 20.75 199
1993 15 11 9 86.75 50.75 16.75 145
1994 20 10 5 85.50 33.00 17.00 125
1995 10 7 3 51.75 22.25 9.00 73
1996 9 5 2 32.00 13.00 3.25 45
1997 19 9 7 78.50 33.50 15.00 124
1998 13 9 6 62.75 33.00 10.75 102
1999 9 6 2 44.50 23.50 6.00 60
2000 19 6 2 67.50 16.75 4.75 70
2001 15 8 2 58.25 18.50 5.00 69
2002 15 8 6 64.75 26.00 9.00 97
AVG 16.3 9.3 4.5 74.7 32.0 8.9
The final table is identical to the preceding one except that it
covers the Eastern North Pacific proper only--from longitude 140W
eastward to the Mexican and Central American coasts. The "days"
parameters--NSD, HD and IHD--do not include portions of cyclones spent
west of 140W. (Note: A similar set of statistics appeared as the
monthly feature in the July, 2000, summary. Those had been calculated
by John Wallace and covered the period 1971-1999. John had calculated
them by hand from the Best Track file, and his methodology was to
include only the storms originating east of 140W, but to include in
the "days" parameters the entire life cycles of the cyclones. An NTC
calculated thusly is also useful in that it reflects the level of
activity generated by the Eastern North Pacific systems. However,
my rather simple software which reads through the NEP Best Track file
isn't set up to do that, and the re-programming necessary to emulate
John's procedure would be too time-consuming at the present moment.)
Eastern North Pacific (East of 140W)
Annual NTC Table
Based on Period 1971-2002
-----------------------------------------
Month NS H IH NSD HD IHD NTC
1971 18 12 6 80.75 36.75 6.00 122
1972 12 8 3 62.50 24.75 2.75 77
1973 12 7 3 51.75 24.00 7.00 81
1974 17 11 2 59.25 18.75 2.25 78
1975 16 8 4 68.75 26.00 5.50 94
1976 14 8 5 57.75 22.50 9.75 99
1977 8 4 0 20.50 5.25 .00 24
1978 18 12 6 73.00 35.25 13.25 134
1979 10 6 4 33.75 13.75 3.25 62
1980 14 7 3 43.75 20.00 2.75 69
1981 15 8 1 55.25 18.25 1.00 62
1982 19 11 4 76.75 33.00 6.00 108
1983 21 12 8 98.00 46.25 15.00 162
1984 18 12 6 93.25 43.50 14.50 147
1985 22 11 7 90.25 37.00 5.75 130
1986 17 9 3 56.25 24.75 5.25 88
1987 18 9 4 66.00 24.75 7.75 101
1988 13 6 1 51.25 18.75 2.25 58
1989 17 9 4 62.75 24.75 5.75 94
1990 20 16 6 115.25 55.50 18.00 177
1991 14 10 5 82.00 42.75 14.00 131
1992 24 14 8 132.75 57.00 18.25 192
1993 14 10 8 73.50 42.25 15.25 143
1994 17 8 4 51.50 14.50 4.25 80
1995 10 7 3 51.75 22.25 9.00 82
1996 9 5 2 32.00 13.00 3.25 50
1997 17 9 7 67.25 33.50 15.00 133
1998 13 9 6 60.75 32.75 10.75 113
1999 9 6 2 35.50 16.25 5.75 60
2000 17 6 2 56.50 15.75 4.75 72
2001 15 8 2 58.25 18.50 5.00 76
2002 12 6 5 48.00 19.25 8.50 86
AVG 15.3 8.9 4.2 64.6 27.5 7.7
A couple of adjustments have been made from the original NS values
obtained from the Best Track file. In 1975 sixteen tropical storms
were named by the Eastern Pacific Hurricane Center in San Francisco--
the agency responsible for issuing warnings in that basin prior to
1988. However, the program reported 17 tropical storms. A hurricane
formed in subtropical latitudes in the Central North Pacific in late
August. The cyclone remained unnamed at the time, but was later added
to the Best Tracks file. The final position in the storm's track,
stilled flagged as tropical, was 138W. However, the latitude was 54N!
It seems highly unlikely that the system was still exhibiting tropical
storm characteristics at latitude 54N in the Eastern Pacific, so I did
not include that storm.
The other adjustment was made for 1982. The San Francisco center
named 19 storms, Aletta through Tara. However, the program reported
only eighteen. The first data point for Tropical Storm Emilia, at
0600 UTC on 13 July, was 10.5N, 140.5E, with 35-kt winds. It seems
likely that a tropical disturbance suddenly intensified and that the
Eastern Pacific Hurricane Center assigned the name Emilia just as it
was crossing 140W. There is also the possibility that the center
position was readjusted westward during post-storm analysis. So I
did count Tropical Storm Emilia as an Eastern North Pacific cyclone,
but all its "days" parameters occurred west of 140W.
*************************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for May: No tropical cyclones
Atlantic Tropical Activity for May
----------------------------------
A quiet month of May followed the first April Atlantic tropical
cyclone on record. Since 1886 twelve tropical storms have formed
during May, with additional tropical depressions and subtropical storms
tracked. The last tropical storm to form in May was Tropical Storm
Arlene in 1981, which formed in the western Caribbean during the first
week of May. Following a May tropical storm in 1887 and a hurricane in
1889, no more May storms were detected until 1932. However, since 1932
the longest gap between May tropical storms has been eleven years (1959
to 1970 and 1970 to 1981). So the Atlantic basin is overdue for a May
tropical storm.
There was an interesting system off the southeast U. S. coast during
the first week of the month which initially seemed to have delusions of
developing into a subtropical storm. A meso-scale convective system
from the Gulf of Mexico had moved to a position off the North Carolina
coast by 2 May where it exhibited some rotation and had generated some
convection near the center. (This information from David Roth.)
According to Bob Hart, the Cyclone Phase Space had initially indicated
possible hybrid or even weak warm-core development, but later runs of
the program had backed off a bit and trended toward neutral or cold-
core evolution. And Chris Fogarty pointed out that with the upper-level
trough open to the northwest of the LOW, it would have been very
difficult for a warm-core cyclone to form.
*************************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for May: 1 tropical storm
Northeast Pacific Tropical Activity for May
-------------------------------------------
For the fourth consecutive year, the Northeast Pacific basin produced
a named tropical cyclone. The only other occasion since 1971 when four
consecutive Mays produced a named storm was 1981-1984. In contrast,
however, to the rather intense Hurricanes Aletta, Adolph and Alma of the
previous three seasons, Tropical Storm Andres of 2003 remained a fairly
weak tropical storm. It did have a rather long life span for a weak
system, tracking almost to the boundary with the Central North Pacific.
The following report on Andres was written by John Wallace of San
Antonio, Texas. A special thanks to John for his assistance.
TROPICAL STORM ANDRES
(TC-01E)
20 - 26 May
-----------------------------------------
A. Storm Origins
----------------
The disturbance that became Tropical Storm Andres may have been
noted in the ITCZ south of the Bay of Tehuantepec as early as 16 May.
However, it is more likely that the system's precursor can be traced to
a disturbance that tracked westward from Central America around the
18th. A LOW was definite in satellite imagery later that day, and the
LOW slowly strengthened over the next 24 hours until it became organized
sufficiently to warrant its upgrade to Tropical Depression One-E at
0300 UTC on 20 May when it was located roughly 475 nm south-southwest of
Acapulco, Mexico. The depression tracked westward under the influence
of a well-defined subtropical ridge to its north. Conditions remained
favorable on the whole for intensification, and the cyclone duly
strengthened to Tropical Storm Andres at 1500 UTC on the 20th while
positioned roughly 550 nm southwest of Acapulco (this was just 12 hours
after the first warning).
B. Storm History
----------------
Andres' quick christening was not the shape of things to come. Even
at its upgrade its center was difficult to locate, and was later found
to be displaced west of the central convection due to westerly shear.
The shear was persistent, and Andres failed to thrive in spite of
optimistic official forecasts.
On the 21st, Andres' unusually swift westward track bent to the west-
northwest as the subtropical ridge weakened and moved east. The
synoptic environment became slightly more favorable, and Andres reached
its peak estimated MSW of 40 kts, with a CP of 1002 mb, at 0900 UTC on
22 May when located some 1025 nm west-southwest of Acapulco. At the time
this intensity estimate was considered conservative. Shear prevented the
storm from strengthening further, however, and Andres fluctuated around
minimal tropical storm strength for the next two days as it raced west-
northwest--indeed, its rapid motion was probably the cause of much of
the net westerly shear. Though it weakened after its peak, the MSW
reached 40 kts twice more, at 0900 UTC on the 23rd and at 2100 UTC on
the 24th, as its convection waxed and waned with the vagaries of its
environment.
Andres' last peak coincided with its crossing of the 26 C isotherm
and entry into a more hostile upper-level environment due to a strong
trough east of the Hawaiian islands. It quickly weakened to a
depression on the 25th as its convection collapsed, while its former
arrow-straight, west-northwesterly track bent back to the west with the
low-level trade winds. The final advisory on Tropical Depression Andres
was issued at 0300 UTC on 26 May with the weakening center located
roughly 925 nm east of Hilo, Hawaii, just shy of the CPHC's AOR. The
cyclone's remnants dissolved rapidly; there was no significant trace of
cyclonic organization by late that day, though its amorphous cloud mass
remnant lingered for a few days thereafter.
C. Damage and Casualties
------------------------
There are no known casualties or damages associated with Tropical
Storm Andres.
(Report written by John Wallace)
*************************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for May: 3 tropical storms **
1 typhoon
** - one of these considered a tropical storm by JTWC only
Northwest Pacific Tropical Activity for May
-------------------------------------------
The Northwest Pacific basin experienced a rather active month of May.
Three tropical storms were named by JMA, and an additional system was
briefly upgraded to tropical storm status by JTWC (and was assigned a
name by PAGASA). The only typhoon of the month was Chan-hom, which
formed deep in the tropics in the Chuuk area and moved northward out of
the tropics, passing well to the east of Guam and the Marianas. Chan-hom
became a rather intense storm with the peak MSW reaching 115 kts (per
JTWC's analysis). Tropical Storms Linfa and Nangka were rather similar.
Each formed in the northeastern South China Sea and followed generally
northeasterly tracks. Linfa/Chedeng moved eastward across northern
Luzon, where its rains were responsible for significant flooding and loss
of life, whereas Nangka/Dodong tracked northeastward, passing between
Luzon and Taiwan. The other system, Tropical Storm 03W (named Batibot
by PAGASA) followed an erratic course northward off to the east of the
southern Philippines.
The summaries on Tropical Storms 03W, Linfa, and Nangka were written
by Kevin Boyle of Stoke-on-Trent, UK. A special thanks to Kevin for
his assistance. Also, a big thanks to Huang Chunliang and Karl Hoarau
for sending along synoptic observations relating to Tropical Storm Linfa.
CORRECTIONS and ADDENDA to APRIL SUMMARY
----------------------------------------
Huang Chunliang pointed out a few errors that I had made in reporting
the observations from Typhoon Kujira:
(1) The original summary reported that Aburatsu, Miyazaki Prefecture,
had recored SSW winds of 32 kts at 24/1700 UTC. The correct time
should read 25/0700 UTC.
(2) The station names "Lan Yu" and "Green Island" are better rendered
as "Lanyu" and "Ludao".
(3) Regarding a 24-hr rainfall total of 342 mm recorded at Tarama on
Okinawa on 24 April, I had indicated that I was not sure of the
applicable time period. This amount was measured between 0000 and
2400 local time (UTC + 9 hrs) on 24 April.
Karl Hoarau pointed out that the pressure readings from Lanyu which
I had identified as SLP--the minimum being 965 mb--were almost certainly
unadjusted station pressure readings. The station is at an altitude of
325 m, and the center of Kujira passed about 55 nm east of the island
per both JMA's and JTWC's warnings. Karl indicated that he had
rechecked infrared and microwave images of the storm and found that the
system's appearance in satellite imagery was nowhere near a Dvorak T4.5,
equivalent to 965 mb.
Finally, Huang Chunliang sent along some rainfall observations from
Taiwan which had been unavailable earlier when he'd sent the original
report. These are as follows:
Station Storm Total (20/1600 - 23/1800 UTC)
----------------------------------------------------------------
Shin-liao, Ilan County 155 mm
Shuang-Lian Pi, Ilan County 143 mm
Tai-on, Hualien County 119 mm
Ilan 90 mm
Daping, Taipei County 85 mm
Lanyu 68 mm
Ludao 64 mm
Keelung 58 mm
A thanks to Chunliang and Karl for sending these corrections and
addenda. I will update the April summary and send a corrected version
to the archive sites.
TROPICAL STORM
(TC-03W / BATIBOT)
17 - 20 May
--------------------------------------
Batibot: PAGASA name, is the name of a Filipino children's television
show similar to Sesame Street
A. Storm Origins
----------------
The origins of Tropical Storm 03W can be traced back to an area of
deep convection, noted in a STWO issued at 1730 UTC, 16 May, located
near 5.6N, 132.2E (approximately 180 nm southwest of Palau). Upper-
level analysis revealed good diffluence aloft and a favourable wind
shear environment while animated infrared imagery indicated the
existence of a possible LLCC. The development potential was described
as poor, but was raised to fair at 17/0600 UTC when animated multi-
spectral satellite imagery revealed cycling but disorganized deep
convection over possible multiple LLCCs embedded within a surface
trough. JMA began issuing warnings at this time, classifying the system
as a 30-kt (10-min avg) tropical depression near 7.1N, 130.5E. The first
JTWC warning at 17/1800 UTC superceded the TCFA issued at 17/1130 UTC.
B. Storm History
----------------
At the time of the first warning, TD-03W was located approximately
80 nm east of Mindanao, Philippines (7.3N, 127.9E.) Initial movement
was toward the west at 5 kts with the MSW set at 25 kts. Animated
infrared satellite and microwave imagery indicated that the LLCC was
continuing to slowly organize with radial deep convection turning
toward the centre of the system. Despite unfavourable wind shear
conditions the MSW was raised slightly to 30 kts at 18/0600 UTC. At
this time, the broad LLCC was moving slowly northward at 2 kts, and
based on QuikScat, SSM/I and synoptic data, was relocated to a position
approximately 210 nm east of Mindanao, Philippines (7.7N, 129.9E).
(JMA also repositioned the centre to near 8.6N, 130.3E.) At this point,
deep convection had been decreasing and TD-03W was suffering from the
effects of the wind shear as evidenced by the partial exposure of the
LLCC east of the deep convection. However, deep convection began to
pick up again, and at 19/0000 UTC JTWC upgraded the system to a 35-kt
tropical storm. The still partially-exposed LLCC was then located
approximately 270 nm east of Mindanao, (9.1N, 130.8E), moving in a
northeastward direction at 7 kts.
PAGASA initiated warnings at 19/0600 UTC and assigned their internal
name Batibot. (Note: No international name was given to this system
as JMA did not regard it as a tropical storm. Neither did any other
agency, including the CWB of Taiwan who had been monitoring the system
through their bulletins since 18/1200 UTC but never forecast tropical
storm intensity. HKO ranked TS-03W as a tropical depression but did not
issue statements. No warnings were issued by NMCC.)
A significant decrease in deep convection was noted at 19/1200 UTC.
and the LLCC became difficult to locate in infrared satellite images.
Subsequently, TS-03W was downgraded to tropical depression status.
The position was estimated to be approximately 325 nm west of Yap
(10.3N, 132.7E). Based on infrared satellite imagery and a 19/1812
UTC TRMM pass, another relocation was required at 1800 UTC. (The
LLCC's position was relocated further northwest to 10.7N, 131.1E.)
Forward motion had become northwestward at 6 kts toward a weakness
caused by a passing shortwave trough. The perspective from the multi-
spectral satellite imagery at 19/2330 UTC was that of a fully-exposed
centre with most of the sheared deep convection concentrated east and
south of the LLCC. A little over six hours later, the situation had not
improved and JTWC issued the final warning at 20/0600 UTC. The final
fix of the very poorly-defined LLCC was approximately 355 nm east-
northeast of Tacloban, Philippines (12.8N, 130.8E.) PAGASA and JMA
ceased writing bulletins at 20/1200 UTC while CWBT continued to issue
advisories until 22/0000 UTC.
C. Damage and Casualties
------------------------
No reports of damage or casualties associated with Tropical Storm
03W/Batibot have been received.
(Report written by Kevin Boyle)
TYPHOON CHAN-HOM
(TC-04W / TY 0303)
18 - 28 May
--------------------------------------
Chan-hom: contributed by Laos, is a kind of tree
A. Storm Origins
----------------
JTWC issued a TCFA at 1500 UTC on 18 May for a disturbance located
approximately 300 nm southwest of Chuuk. (The disturbance was not
mentioned in the daily STWO on 15 May, so must have begun to develop
on either the 16th or 17th--I am missing the STWOs for those dates.)
Deep convection was cyclic, but organization had improved during the
previous six hours. The convection was near the broad LLCC, and a
200-mb analysis indicated moderate vertical shear and good diffluence
aloft. Also, a westerly wind burst was enhancing winds to the south
of the system. The first JTWC warning on TD-04W was issued at 19/0000
UTC and placed the center roughly 470 nm southeast of Guam, moving
north at 5 kts. Visible and microwave imagery indicated improving
organization of the LLCC. (JMA had classified the system as a tropical
depression earlier at 1200 UTC on the 18th.)
B. Storm History
----------------
A U. S. Air Force Reserves' reconnaissance plane investigating the
depression found a pressure of 1003 mb and maximum FLW of 42 kts in the
southeast quadrant at 19/0508 UTC, and 50 kts in the southern quadrant
at 0603 UTC. JTWC upgraded TD-04W to tropical storm status in the
second warning, issued around 0900 UTC. At 0600 UTC the center was
located approximately 140 nm west-southwest of Chuuk, moving northeast-
ward at 4 kts. TS-04W remained at 35 kts for the remainder of the 19th
as it trekked slowly north and northeastward a little over 100 nm west
of Chuuk. A weakness was seen developing in the low to mid-level ridge
to the north, enhanced by a mid-latitude trough translating eastward
from the Asian continent. The tropical cyclone was forecast to continue
its general northward motion toward this weakness developing in the
ridge.
By 1200 UTC on 20 May the tropical storm had reached a position about
80 nm west-northwest of Chuuk. Satellite CI estimates ranged from 35 to
55 kts, and a 20/1118 UTC SSM/I pass indicated that the system had
become more concentric with good radial outflow and spiral banding
features while remaining under a very favorable upper-level environment.
JTWC upped the MSW to 55 kts at 1200 UTC, and JMA upgraded the cyclone
to tropical storm status, assigning the name Chan-hom. (NMCC and CWBT
also upgraded the system to tropical storm status at 20/1200 UTC.)
A reconnaissance aircraft had made several fixes during the early hours
of the 20th, finding a maximum FLW of 67 kts in the southern quadrant
at 20/0326 UTC with a CP of 996 mb. On the 21st Tropical Storm Chan-hom
continued to track slowly northward along the western periphery of a
mid-level ridge situated to the northeast, moving toward the afore-
mentioned weakness in the subtropical ridge. The storm slowly gained
in intensity as the day wore on--by 1800 UTC JTWC and NMCC were reporting
60 kts (1-min and 10-min averages, respectively) while JMA and CWBT were
estimating 55 kts (10-min avg).
At 22/0000 UTC Chan-hom was located about 380 nm east-southeast of
Guam, trudging northward at 7 kts. A 21/2204 UTC SSM/I pass indicated
the development of a banding eye feature, and CI estimates had reached
55 and 65 kts. Based on this, JTWC upgraded Chan-hom to a 65-kt typhoon
at 0000 UTC, but the intensity remained pegged at minimal typhoon
intensity for another 24 hours. (NMCC and CWBT upgraded Chan-hom to
typhoon status at 23/0000 UTC, and JMA did so at 23/0600 UTC.) U. S.
Air Force Reserves' reconnaissance flights into Chan-hom during the early
hours of the 22nd found a peak FLW of 67 kts in the eastern quadrant
at 22/0330 UTC, and the pressure had dropped to 983 mb by 0538 UTC.
By 23/0000 UTC the typhoon had reached a position 380 nm north-
northeast of Guam, and JTWC upped the MSW to 85 kts based on CI estimates
ranging from 65 to 102 kts. Chan-hom at this time was sporting a 20-nm
diameter eye. The storm increased steadily in intensity and by 1800 UTC
had reached its peak intensity of 115 kts, based on CI estimates of 115
and 127 kts. (The peak 10-min avg MSW values for Chan-hom from JMA,
NMCC and CWBT were 85, 75 and 85 kts, respectively.) Gales reached out
around 100 nm from the 10-nm symmetrical eye, and the radius of 50-kt
winds was 40 nm. JMA estimated the minimum CP at 940 mb. Typhoon
Chan-hom was located approximately 450 nm east-northeast of Guam at
this time, and had turned to a north-northeastward heading at 10 kts.
Chan-hom maintained its peak intensity through 25/0600 UTC (per JTWC's
warnings) as CI numbers remained at 115 kts. However, as early as 0000
UTC on the 24th animated water vapor imagery showed some dry air
entrainment into the southeastern quadrant, and the eye had become
irregular and ragged in appearance by 24/1200 UTC. The storm was then
located approximately 800 nm west of Wake Island, and satellite imagery
suggested that the poleward outflow was being temporarily enhanced by
an approaching deep mid-latitude trough. Chan-hom's forward motion
began to accelerate to the northeast as it became increasingly influenced
by the westerlies. At 24/1800 UTC it was moving northeastward at 17 kts.
JTWC reduced the intensity to 90 kts at 25/0600 UTC with Chan-hom
then located about 660 nm west-northwest of Wake Island. The dry air
entrainment had continued, vertical shear was increasing, and the system
was starting to link up with the mid-latitude trough. Extratropical
transition was underway, and at 25/1800 UTC JTWC lowered Chan-hom's
MSW to minimal typhoon intensity of 65 kts. By 26/0000 UTC the storm
had lost much of its convection, and at 0600 UTC all the warning agencies
downgraded Chan-hom to tropical storm status (except NMCC, which main-
tained the system as a typhoon for six more hours). Chan-hom was then
located over 1100 nm west of Midway Island, scooting northeastward at
22 kts.
Even though the system was becoming extratropical, some tropical
features lingered. At 1200 UTC the JTWC warning remarked that Chan-hom
remained vertically stacked with some tropical banding features still
evident. By 1800 UTC the storm was located about 950 nm west-northwest
of Midway Island, and the LLCC had become decoupled from the remaining
deep convection. JTWC declared Chan-hom extratropical at 27/0000 UTC
when located about 850 nm west-northwest of Midway, still moving north-
eastward at 22 kts, and JMA classified the former typhoon as an extra-
tropical system six hours later. The remnants of Chan-hom continued to
weaken and move eastward, crossing the International Dateline shortly
before 28/1200 UTC. The final reference to the system in JMA's High
Seas Bulletins, at 28/1800 UTC, placed a weak 25-kt LOW several hundred
miles north of Midway Island.
Early in its history Chan-hom posed a potential threat to the island
of Guam. Fortunately, this failed to materialize, sparing the island
from what could have been the third typhoon strike in less than a year.
Chan-hom did, however, have an effect on the island. After the typhoon
had passed by Guam well to the east, the resulting wind shift began to
redirect a plume of ash from the continuing eruption of a volcano on
Anatahan, an uninhabited island 70 nm north of Saipan, toward Guam.
Guam's Environmental Protection Agency issued a volcanic haze advisory
for the island, urging residents, especially those with respiratory
problems, to take precautions. In addition to the ash, sulfur dioxide
and other volcanic gases reacted with oxygen and atmospheric moisture to
produce volcanic smog, or vog, and acid rain. The vog can aggravate
pre-existing respiratory ailments, and the acid rain damages crops.
C. Damage and Casualties
------------------------
No damage or casualties are known to have resulted from Typhoon
Chan-hom.
(Report written by Gary Padgett)
TROPICAL STORM LINFA
(TC-05W / STS 0304 / CHEDENG)
25 - 31 May
-------------------------------------------------
Linfa: contributed by Macau, is the Macanese name for the lotus,
an Oriental water lily with pinkish flowers and large leaves
Chedeng: PAGASA name, is a Filipino nickname for either males or
females; it is also a term used for the German car Mercedes
Benz
A. Storm Origins
----------------
An area of convection developed and persisted near 14.1N, 114.9E, or
approximately 350 nm west of Manila, Philippines. This was included in
JTWC's STWO issued at 1900 UTC on 23 May. Animated enhanced infrared
satellite imagery revealed that the convection was associated with a
developing LLCC located in the southeastern quadrant of an anticyclone
anchored over the Gulf of Tonkin with divergence aloft, as evidenced
by a 200-mb analysis. Development potential for the next 24 hours was
poor. A day later, at 24/1900 UTC, the potential was upgraded to good
and a TCFA issued. QuikScat data at this time revealed that the LLCC
had consolidated (with deep cycling convection) and was being fueled by
a westerly wind burst. Vertical wind shear in the area was weak, an
ideal condition necessary for further development.
JTWC kicked off Tropical Storm Linfa's career with the first warning,
issued at 0000 UTC on 25 May. JMA started issuing bulletins six hours
later. At the same time PAGASA also began writing warnings on Chedeng,
that agency's third named system of the year. (At 25/0600 UTC PAGASA
upgraded Chedeng to a tropical storm.) The depression was moving very
slowly northwestward away from the Philippines at 3 kts at this time, and
during the 25th Chedeng traced a slow, labourious cyclonic loop. The
expectations were that once TD-05W had intensified beyond its weak,
shallow stage, it would move slowly eastward towards Luzon along the
northern periphery of the low to mid-level near-equatorial ridge axis
located to the south. The slow erratic motion allowed for some
strengthening, and JTWC upgraded the depression to a 45-kt tropical storm
on Warning #4, issued at 25/1800 UTC. TS-04W was named Linfa six hours
later when JMA also upgraded the system to tropical storm status.
B. Storm History
----------------
At 26/0000 UTC Tropical Storm Linfa was still almost stationary near
16.1N, 118.2E, or approximately 185 nm northwest of Manila. (Note: All
Asian agencies were warning on Linfa by this time as a tropical storm
with the introduction of CWBT and HKO, which had begun issuing advisories
at 25/0600 UTC and 25/1200 UTC, respectively. NMCC began releasing
statements at 26/0300 UTC, classifying Linfa as a 40-kt tropical storm
(10-min avg) three hours later.) This very slow motion gave the
opportunity for the tropical cyclone to slowly develop and intensify a
little more, and by 26/1800 UTC the MSW was up to 55 kts. At this time
Linfa began moving toward the east to begin its attack on the
Philippines.
At this juncture, Linfa failed to intensify further, and at 0000 UTC,
27 May, was making landfall on Luzon as a 55-kt tropical storm. Moving
eastward at 7 kts, Tropical Storm Linfa crossed the northern Philippine
island of Luzon (weakening to 35 kts in the process) and had re-emerged
back over water by 27/1800 UTC. At 28/0000 UTC Linfa was downgraded to
a 25-kt depression. (JMA had dropped the system to a 35-kt tropical
storm, but at 28/0000 UTC upped the intensity slightly to 40 kts (10-min
avg). The remaining Asian TCWCs also retained tropical storm status.)
The JTWC warning (#13) issued at this time noted that the main centre
was weakening and that a new LLCC was developing near 18.6N, 123.6E,
based upon careful analysis of a 27/2139 UTC QuikScat pass. This was
forecast to become the dominant centre within 12 hours. All the Asian
TCWCs began following this new LLCC as of 28/0000 UTC while JTWC
continued to track the old centre through 28/1800 UTC. This is the
primary reason for the large deltas in centre position and intensity on
the 28th and JTWC's downgrade to tropical depression status. The mid-
level portion of the original circulation had coupled up with the new
LLCC by 28/1200 UTC. HKO issued their final warning on Linfa, still as
a 35-kt tropical storm, at 28/1500 UTC. The agency did upgrade the
system back to severe tropical storm status after it had exited their
area of warning responsibility.
After the amalgamation of both LLCCs, JTWC relocated the position of
the new LLCC at 29/0000 UTC, resulting in a jump to 22.3N, 125.8E, or
approximately 250 nm south-southwest of Naha, Okinawa. Linfa was at
this time moving on a north-northeasterly heading at 11 kts. A 28/2331
UTC SSM/I pass showed that Linfa was becoming more organized with
distinct banding features and increased convection consolidating around
the LLCC. By 29/0600 UTC the MSW had increased to 35 kts and Linfa was
once again upgraded to a tropical storm. This was based on banding
features observed in recent SSM/I and animated multi-spectral imagery.
However, the system was seen to be asymmetrical, partially-exposed, and
with almost all the deep convection confined to the eastern semicircle.
The system then accelerated northeastward at a faster pace of 16 kts
which took it out of PAGASA's AOR by 29/1800 UTC. Accordingly, PAGASA
ceased writing bulletins. The strengthening Linfa passed 140 nm south-
east of Naha, Okinawa around this time.
Twelve hours later, Linfa reached a secondary peak of 60 kts (based
on WC-130 reconnaissance data), although recent animated multi-spectral
satellite imagery indicated that the LLCC remained partially-exposed.
Turning to a more northerly heading at 23 kts, Linfa began to slowly
weaken, and by the time JTWC issued their final warning at 30/1200 UTC,
the MSW had fallen to 50 kts. At this time animated enhanced infrared
and water vapor satellite imagery, and a 30/1751 UTC TRMM pass, revealed
that the system had completed extratropical transition. The final
warning placed the centre of Linfa approximately 120 nm south of Iwakuni,
Japan, or near 32.0N, 132.0E. NMCC and CWBT both ended their warning
coverage at 31/0000 UTC while JMA monitored the extratropical system for
a further 12 hours.
Continuing northward, the centre of the extratropical Linfa made
landfall near Uwajima City, Japan, around 0500 local time on May 31.
The final position of the storm plotted by JMA was near 36.0N, 135.0E,
with the centre just about to enter the Sea of Japan.
C. Meteorological Observations
------------------------------
1. Philippines
--------------
Karl Hoarau passed along the following surface observations in
association with Linfa. (A thanks to Karl for sending the information.)
The coastal station of Botolan (WMO 98324) recorded 153 mm during
the 24-hour period from 26/0000 UTC to 27/0000 UTC. The station also
reported 68 mm between 0000 and 0600 UTC on the 27th.
Karl also passed on some more rainfall data listed below:
Period from 26th 0000 UTC to 28th 0000 UTC
Location WMO Code Rainfall (mm)
-------------------------------------------
Cabanatuan 98330 225
Subic Bay 98426 239
Sangley Point 98428 239
Iba 98324 289
Baguio 98328 364
Dagupan* 98325 723
*At this station, 378 mm were recorded on the 27th from 0600 to 1200
UTC, and 251 mm on 27th from 1200 to 1800 UTC. This means that 629 mm
were recorded in 12hrs!
Tropical Storm Linfa passed 50 nm west-northwest of the station
WMO 47945 (25.8N, 131.2E) around 0100 UTC-0200 UTC on 29 May. The
station reported a south wind of 32 kts (10-min avg) and a minimum SLP
of 991.2 mb at 0300 UTC, 30th May. From 1200 UTC on the 29th to 0000
UTC on the 30th 73 mm of rainfall was reported.
Dagupan (WMO 98325), near the west coast of Luzon, reported a minimum
SLP of 989.0 mb at 27/0200 UTC, but a wind speed of only 10 kts was
recorded. This station is protected somewhat by the mountains to the
east which act as a barrier to winds from the northeast through the
southeast.
2. Japan
--------
Huang Chunliang has sent an extensive amount of information from
several Japanese stations. (A thanks to Chunliang for sending along
the observations.)
a. Rainfall observations
------------------------
JMA station reports exceeding 200 mm were fairly common with one
report of over 300 mm. Mie, Osawe (WMO 47663) reported 464.0 mm on the
31st of May (exact period unknown). The following tables include only
24-hour reports exceeding 100 mm. The recording period is the
calendar date in local time: UTC + 9 hours.
WMO stations in:
----------------
Okinawa
-------
No stations recorded rainfall of >100 mm.
Japan
-----
Prefecture Station WMO Code Rainfall (mm) Date (May)
---------- ------- -------- ------------- ----
Miyazaki Nobeoka 47822 199.5 30th
Miyazaki Miyazaki 47830 125.0 30th
Nagasaki Izuhara 47800 196.5 30th
Nagasaki Fukue 47843 137.5 30th
Tokushima Tokushima 47895 147.5 31st
Shimane Saigo 47740 152.0 31st
Shimane Hamada 47755 107.5 31st
Mie Owase 47663 464.0 31st
Aichi Irako 47653 110.0 31st
Shizuoka Hamamatsu 47654 122.5 31st
Shizuoka Omaezaki 47655 216.0 31st
Shizuoka Shizuoka 47656 159.5 31st
Yamanashi Kawaguchiko 47640 110.5 31st
JMA stations (only amounts greater than 200 mm are given):
----------------------------------------------------------
Prefecture Station JMA code Rainfall (mm) Date (May)
---------- ------- -------- ------------- ----------
Miyazaki Hyuga 87181 208 30th
Miyazaki Mikado 87206 241 30th
Miyazaki Mitate 87046 209 30th
Miyazaki Kitakata 87136 287 30th
Miyazaki Nakagoya 87126 279 30th
Miyazaki Wanitsuka 87436 281 30th
Miyazaki Fukase 87461 277 30th
Kochi Nakamura 74456 244 30th
Kochi Naruyama 74176 212 30th
Kochi Sakawa 74166 262 30th
Kochi Funato 74237 217 30th
Kochi Hongawa 74056 252 31st
Kochi Yanase 74151 204 31st
Tokushima Kito 71251 224 31st
Tokushima Fukuharaasahi 71211 238 31st
Wakayama Irokawa 65311 231 31st
Mie Kayumi 53231 212 31st
Mie Kiinagashima 53326 235 31st
Mie Atashika 53401 217 31st
Mie Miyagawa 53321 268 31st
Mie Mihama 53416 370 31st
Shizuoka Amagi 50427 296 31st
b. Sustained Wind Measurements
------------------------------
Station Minamidaitojima on Okinawa (WMO 47945; 25.83N, 131.23E;
Alt 15 m) recorded a peak MSW of 34 kts from the south-southeast at
0200 UTC on 30 May with a minimum SLP of 991.2 hPa reported an hour
later at 0300 UTC.
In Japan, Yakushima, Kagoshima (WMO 47836; 30.38N, 130.67E; Alt 36 m)
reported a maximum MSW of 31 kts and a SLP of 986.5 hPa on 30 May at
0900 UTC and 1300 UTC, respectively. Aburatsu, Miyazaki (WMO 47835;
31.57N, 131.42E; Alt 3 m) measured a MSW of 37 kts from the northeast at
1300 UTC, 30 May. The station reported a MSLP of 981.5 hPa at 30/1600
UTC. Muruotomisaki, Kochi (WMO 47899; 33.25N, 134.18E; Alt 185 m)
recorded a MSW of 61 kts from the east-northeast at 30/1600 UTC. Later,
at 31/0600 UTC, a minimum SLP of 990.5 hPa but with winds of only 18 kts
was recorded.
Staying in Japan, WMO 47892 (Uwajima, Ehime; 33.23N, 132.55E; Alt 2 m)
measured a SLP of 984.6 hPa at 30/1900 UTC and 30/2000 UTC, but the
sustained wind maximum only reached 27 kts at 0800 UTC, 31 May. Okayama,
Okayama (WMO 47768; 34.65N, 133.92E; Alt 3 m) reported a MSW of 30 kts
from the east at 30/2200 UTC and a minimum SLP of 988.6 hPa nine hours
later.
Shionomiski, Wakayama (WMO 47778; 33.45N, 135.77E; Alt 73 m) measured
a MSW of 26 kts (from the east) at 30/1700 UTC and a SLP of 993.4 hPa at
31/1000 UTC. Tsu, Mie (WMO 47651; 34.73N, 136.52E; Alt 3 m) recorded
east-southeast winds of 34 kts at 30/1900 UTC and a SLP of 993.8 hPa
for 2 hours (1200 and 1300 UTC on 31 May). JMA station 65036 (34.28N,
135.00E, Alt 43 m) in Tomogasima, Wakayama, reported near-gales of up to
31 kts for a lengthy period between 0200 UTC to (and including) 0800 UTC,
31 May.
c. Peak Gusts
-------------
Several stations recorded peak gusts exceeding gale force with a few
exceeding storm force and one of hurricane intensity and another just
short of hurricane intensity. Peak gusts exceeding 48 kts (24.6 m/sec)
include (dates are local time):
30th May:
---------
Prefecture Station WMO ID Alt (m) Peak Gust (kts)
-----------------------------------------------------------------------
Okinawa Minamidaitojima 47945 28 60
Kagishima Tanegashima 47837 17 48
Kagoshima Naze 47909 3 49
Miyazaki Aburatsu 47835 3 57
Kochi Sukomo 47897 2 50
Fukui Tsuruga 47631 2 61
31st May:
---------
Prefecture Station WMO ID Alt (m) Peak Gust (kts)
-----------------------------------------------------------------------
Miyazaki Miyazaki 47830 9 52
Kumamoto Asosan 47821 1142 60
Kochi Kochi 47893 1 48
Kochi Muruotomisaki 47899 185 76
Kochi Shimizu 47898 31 64
Ehime Uwajima 47892 2 49
Tokushima Tokushima 47895 2 56
Shimane Saigo 47740 27 51
Shimane Matsue 47741 17 55
Shimane Hamada 47755 19 51
Okayama Okayama 47768 3 51
Hyogo Kobe 47770 5 51
Hyogo Sumoto 47776 109 54
Mie Tsu 47651 3 50
Niigata Aikawa 47602 6 52
d. Observations Highlighted in JMA's Local Warnings
---------------------------------------------------
1. TC Warning #41: Tosashimizu, Kochi, recorded a peak gust of 62 kts
at 30/1410 UTC.
2. TC Warning #51: Mihama, Mie, recorded 93 mm of rain during the
one-hour period ending at 30/2000 UTC. Also, Owase, Mie, reported
80 mm during the same period.
3. Torrential Rain Warning #1 (after Linfa was declared XT): Omaezaki,
Shizuoka, recorded 51 mm of rain during the one-hour period ending
at 31/0100 UTC.
e. Reconnaissance Aircraft Reports
----------------------------------
Reconnaissance aircraft reported a maximum flight-level wind of 34 kts
in the southern quadrant at 0239 UTC, 30 May. The lowest CP extrapolated
from 450 m was 983 mb.
D. Damage and Casualties
------------------------
The death toll reported from the Philippines currently stands at 41
dead, 16 injured, and 10 are still reported missing. Nine of the 41
killed (in the Illoilo and Bicol Regions), based on data released by the
Philippines' National Disaster Coordinating Council (NDCC), were
attributed to the flooding caused by the heavy rains generated by the
southwest monsoon, enhanced by Linfa/Chedeng.
A total of 20 evacuation centres were set up to cope with 2548
persons forced to leave their homes. A total of 2269 houses were
damaged and 206 destroyed.
Cost estimates so far include:
Agriculture/livestock - 66.7 million pesos
Fisheries - 83.4 million pesos
Infrastructure - 42.9 million pesos
NDCC's final report on the effects of Linfa/Chedeng can be found at:
http://www.ndcc.gov.ph/media5.htm>
Some additional articles on the storm's effects in the Philippines
can be found at the following URL:
http://www.reliefweb.int/w/rwb.nsf/vLND>
(Report written by Kevin Boyle with significant contributions by
Huang Chunliang and Karl Hoarau)
TROPICAL STORM NANGKA
(TC-06W / STS 0305 / DODONG)
31 May - 4 June
------------------------------------------------
Nangka: contributed by Malaysia, is the Malaysian name for the
jackfruit, an oval-shaped yellow fruit very popular locally
Dodong: PAGASA name, is a Filipino male nickname
A. Storm Origins
----------------
Tropical Storm Nangka formed in a similar position to its predecessor,
Tropical Storm Linfa, near 17.8N, 117.2E, or approximately 185 nm west of
northern Luzon, Philippines, at 1200 UTC on 31 May (the time of the first
warnings from both JTWC and JMA). At this time the system was moving
slowly northwestward at 4 kts. PAGASA had been following the fortunes of
this system through their bulletins since 31/0000 UTC, dubbing the
cyclone Dodong and setting the MSW at 25 kts (10-min avg). HKO also
took an interest six hours later with their first written statement at
31/0600 UTC.
Initially, the LLCC of TD-06W was difficult to locate due to the weak,
shallow nature of the system, but the combination of QuikScat, animated
enhanced infrared satellite imagery and microwave satellite images
revealed that the centre was organizing slightly south of the 31/1200 UTC
position. Therefore, the coordinates of TD-06W were altered accordingly
to 17.2N, 116.8E, or 210 nm west of Luzon with the primary rainband now
located to the south of the LLCC. The MSW at this time had increased a
little to 30 kts, but the microwave data and water vapor satellite images
indicated that dry air was entraining into the system from the north and
west. PAGASA temporarily halted tropical cyclone warnings on Tropical
Depression Dodong at this time.
B. Storm History
----------------
By 0000 UTC on 1 June Tropical Depression 06W/Dodong's movement had
become a very sluggish northeast crawl at 1 kt. The Prognostic Reasoning
issued at this time (by JTWC) called for an acceleration of the system
on this northeasterly heading later in the forecast period as TD-06W
moved into the controlling influence of the mid-latitude westerlies. The
system had a day or so left to intensify, and at 01/0600 UTC, JTWC, JMA,
HKO and CWBT all upgraded Dodong to a 35-kt tropical storm. PAGASA
resumed warnings on Dodong as a 35-kt storm and NMCC followed with an
upgrade to tropical storm status at 01/900 UTC. NMCC had begun
monitoring the system as a tropical depression at 01/0000 UTC, as did
GRMC (Guangzhou). (Huang Chunliangs's note: It should be noted that
once NMCC upgrades a system to a tropical storm, GRMC will begin to copy
the bulletins from NMCC. All the Asian TCWCs implement a 10-min avg for
the MSW). Tropical Storm Nangka/Dodong began the expected acceleration
toward the northeast, and at 01/1800 UTC animated infrared satellite
imagery revealed an increase in deep convection over the LLCC.
At 0000 UTC on 2 June Nangka was located near 19.9N, 119.2E, or 150 nm
southwest of Taiwan, moving northeastward at 10 kts with a MSW of 45 kts
near the centre. A peak intensity of 50 kts was reached as it bypassed
the island of Taiwan about 64 nm to the southeast at 02/1200 UTC. The
forward speed had by then increased to 21 kts. A 02/1144 UTC SSM/I pass
revealed an exposed LLCC to the south of the remaining deep convection.
The warning issued at 1800 UTC on 2 June downgraded Nangka to tropical
depression intensity, noting that the system was moving east-
northeastward at 16 kts. The LLCC was partially-exposed 75 nm southwest
of the deep convection, and the system was rapidly becoming extra-
tropical. The final warning by JTWC was issued at 02/0000 UTC after the
system was adjudged to have taken on complete extratropical
characteristics and was starting to acquire a frontal system of its own.
This final advisory placed the poorly-defined LLCC near 23.0N, 125.2E, or
225 nm southwest of Naha, Okinawa, and moving east-northeastward at
20 kts. JMA's final advisory at 04/0600 UTC placed the LOW near 30N,
136E. HKO and NMCC ceased their warning coverage at 03/0000 UTC and
04/0000 UTC, respectively, while CWBT also stopped writing bulletins at
04/0000 UTC. PAGASA issued no more advisories after 03/0600 UTC.
C. Damage and Casualties
------------------------
There are no reports of casualties or damages associated with
Tropical Storm Nangka/Dodong.
(Report written by Kevin Boyle)
*************************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for May: 1 tropical cyclone of hurricane intensity
North Indian Ocean Tropical Activity for May
--------------------------------------------
The North Indian Ocean experiences two tropical cyclone seasons each
year, one in the spring and the other in the fall, with very little
tropical cyclone activity during the months of July-September. During
the spring season, May is the month most likely to see tropical activity,
and May of 2003 was no exception. The first tropical cyclone of the year
formed several hundred miles east of Sri Lanka on 10 May and operated
over Bay of Bengal waters until it finally made landfall in Myanmar on
the 19th. The system, designated as Tropical Cyclone 01B by JTWC and
as BOB0301 by IMD, reached hurricane intensity on the 12th for about
24 hours. After weakening and remaining at minimal tropical storm
intensity for several days, the cyclone was rapidly intensifying once
again as it made landfall in Myanmar.
The report on TC-01B was written by John Wallace--a special thanks to
John for his assistance.
TROPICAL CYCLONE
(TC-01B)
10 - 19 May
------------------------------------
A. Storm Origins
----------------
The disturbance that became Tropical Cyclone 01B may have been
evident as early as 6 May as an enhanced region of convection in an
active monsoon trough over the Bay of Bengal. Definite cyclonic
organization was evident on the 7th, though it waxed and waned over the
following days as the disturbance remained nearly stationary. The
JTWC's Joint Metoc Viewer (JMV) track picks it up as a depression-
strength LOW on the 8th when it was roughly 850 nm southeast of Madras,
India. Around this time the system ended its stationary mode and began
a persistent and slow north-northeasterly track. The LOW's organization
improved on the 10th and JTWC issued their first warning on TC-01B at
10/1200 UTC with an initial warning intensity of 30 kts. According to
the JMV track, TC-01B reached tropical storm strength at 1800 UTC that
day when located approximately 575 nm south-southeast of Madras.
B. Storm History
----------------
The second JTWC warning, at 11/0000 UTC, upped the MSW to 50 kts.
The cyclone was then located about 475 nm east-southeast of Madras, or
about 375 nm east of Sri Lanka. Conditions for TC-01B's intensification
were highly favorable with very warm SSTs and a large, well-defined
upper-level ridge with excellent divergence aloft. Things looked as if
the cyclone was set to become intense and a possible scourge to the
vulnerable Bengal shores. The cyclone strengthened steadily--after a
brief hiatus in the trend, its MSW peaked at 65 kts at 1200 UTC on
12 May some 400 nm east of Madras as it plodded steadily towards the
East Indian coast. (More discussion about the peak intensity follows
in Section E.)
The cyclone's star was quick to fall, however. The strong upper-level
ridge to its north induced easterly shear across the system on the same
day it peaked, bringing it below hurricane/typhoon strength by late on
the 13th. Steering currents weakened as well, slowing its forward motion
and turning the cyclone onto an erratic, approximately northward course.
The synoptic situation did not improve, and by late on the 14th a
combination of easterly shear and dry air entrainment had almost
completely dissipated the cyclone's convection save for a sheared
convective core over its center. The system struggled to maintain
minimal tropical storm status from the 14th into the 16th, even as it
continued to generate strong convection.
This particularly bleak time in TC-01B's life corresponded with a
collapse of steering currents that began late on the 14th, and which left
the storm quasi-stationary for the next two days. On the 16th, however,
TC-01B was allowed to recover as it broke out of the stall and tracked
west-southwestward. The system strengthened slightly on the 16th, but
faltered again later that day. The cyclone remained weak as the track
bent first westward, then northwestward into the 18th, drawing a bead on
the Myanmar (Burma) coast. A ridge to its east finally turned TC-01B
northward, whereupon it began a belated and final intensification trend,
even after having briefly weakened to depression strength on the 18th.
The cyclone strengthened quickly once it had the chance; it is perhaps
just as well that it made landfall when it did, at roughly 1000 UTC on
19 May, very near Kyaukpyu, Burma, with a MSW of around 50 kts.
Tropical Cyclone 01B weakened quickly after landfall due to land
interaction and increased shear, and the JTWC issued its last warning on
the system at 1800 UTC on 19 May as it broke up over Myanmar roughly
275 nm north-northeast of Yangon (Rangoon). There was no trace of
TC-01B's remnants in satellite imagery by the 21st.
C. Meteorological Observations
------------------------------
Huang Chunliang sent a few rainfall and wind observations--a thanks
to Chunliang for sending the information. Included were a couple of
24-hour rainfall accumulations from Tamilnadu State, India. Pamban
measured 57 mm on 13 May (local time). On the 14th (local time), the
stations of Parangipettai and Adiramapatnam recorded 70 mm and 98 mm,
respectively.
A ship with call sign VWTL reported northerly winds of 33 kts at
13/0000 UTC when located near 13.6N, 83.6E. Six hours later the same
ship reported northerly winds of 42 kts while located near 12.6N,
82.8E. At 0000 UTC on 16 May ship VWTT, located near 12.5N, 87.2E,
reported southwesterly winds of 35 kts. (The averaging period for
these winds is unknown.)
D. Damage and Casualties
------------------------
There are no reports of damage or casualties in Myanmar associated
with the landfall of Tropical Cyclone 01B. The country of Sri Lanka
experienced heavy monsoonal rains during early May which led to that
nation's most disastrous flooding since 1947 with over 200 persons
perishing in the floods and landslides. TC-01B was located a few
hundred miles to the east of northern Sri Lanka during this period, but
the heavy rains do not appear to be directly associated with the cyclone.
Many articles about the flooding and relief efforts can be found at the
following URL: http://www.reliefweb.int/w/rwb.nsf/vLND>
E. Discussion
-------------
Not surprisingly, TC-01B's peak intensity is a matter of some
conjecture. According to the final JMV track, the peak intensity was
65 kts, which translates to an estimated CP of 976 mb using the JTWC's
MSW-CP relation chart first worked out by Atkinson and Holliday in 1977.
This estimate agrees well with the minimum CP estimate of the IMD
(980 mb). The peak MSW at this time, however, is not tabulated, though
for data points bracketing the minimum CP, the MSW is estimated at
65 kts. Of course, one must factor in the averaging time the IMD uses
for reporting MSW, which is unknown to me. (Editor's Note: The IMD
does not attempt to modify the Dvorak scale intensities; hence, a 1-min
averaging period is implied.) On the whole, the IMD and JTWC tracks
agree well.
The track from the Thai Meteorological Department (TMD) is more
interesting--it reports the peak MSW of TC-01B as 60 kts from 0300 to
1500 UTC on the 13th, and is slightly more liberal with the intensity on
the 14th. If the TMD uses the same MSW averaging period as the JTWC, the
agreement is once again very good. If they use a 10-min averaging
scheme, however, then the estimated peak 1-min avg MSW goes up to 70 kts.
Even so, the overall picture of the estimates from the various agencies
show very good agreement on what was otherwise a well-behaved system,
even if perhaps difficult to forecast.
(Report written by John Wallace with a few additions by Gary Padgett)
*************************************************************************
SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E
Activity for May: 1 tropical cyclone
Southwest Indian Ocean Tropical Activity for May
------------------------------------------------
For the second year in a row, a late-season tropical storm formed
in the Southwest Indian Ocean and reached tropical cyclone (hurricane)
intensity. And for the second consecutive year, Madagascar experienced
damage from a late-season tropical cyclone. In May of 2002 Tropical
Cyclone Kesiny struck the northern tip of the island nation, causing
more than 30 fatalities. In May of 2003, a more intense Tropical
Cyclone Manou struck the eastern coast, leaving more than 70 dead and
practically destroying the city of Vatomandry. Manou almost reached the
intense tropical cyclone level of 90 kts (10-min avg), and was very
unusual in that it was a fairly intense cyclone south of the 19th
parallel so late in the season.
TROPICAL CYCLONE MANOU
(MFR-16 / TC-28S)
2 - 10 May
------------------------------------------
Manou: contributed by Madagascar
A. Storm Origins
----------------
An area of convection in the Southwest Indian Ocean began to develop
around 28 April, and by 1800 UTC on the 29th was located about 400 nm
southwest of Diego Garcia. Animated enhanced infrared and multi-
spectral satellite imagery revealed a LLCC; deep convection was cyclic.
A 200-mb analysis indicated low to moderate vertical shear and moderate
diffluence aloft. Twenty-four hours later the disturbance was in the
same general area with little change in organization noted. By 1400 UTC
on 1 May the system was located approximately 540 nm west-southwest of
Diego Garcia. Deep convection continued to organize around the LLCC and
outflow was favorable. Strong vertical shear was located to the north
and south of the system, but it appeared to be tracking westward away
from the effects of the shear. The potential for development was
upgraded to fair.
At 0800 UTC on 2 May the disturbance was located about 500 nm west-
southwest of Diego Garcia. Deep convection was still cyclic, but an
upper-level analysis indicated that the system was still located under
a ridge axis with favorable outflow. A new area of convection had
formed about 450 nm northeast of Antsiranana, Madagascar, with deep
convection organizing around a LLCC and with favorable outflow aloft.
JTWC assessed the development potential for the new disturbance as
fair also. At 1200 UTC MFR issued the first bulletin for the eastern-
most system, numbering it as Tropical Disturbance 16, while at 1400 UTC
JTWC issued a TCFA for the second, or westernmost disturbance.
At 0400 UTC on 3 May, JTWC issued a TCFA for the original disturbance
(MFR-16). The system was then centered approximately 630 nm northeast of
Mauritius. Deep convection had continued to build over the LLCC, and
recent microwave imagery indicated a significant increase in convective
organization. JTWC issued the first warning on TC-28S at 1200 UTC,
locating the center roughly 530 nm northeast of Mauritius, moving south-
southwestward at 9 kts. Animated multi-spectral imagery indicated
significant convective bands surrounding an improved LLCC. A low to
mid-level ridge to the northeast and the second tropical circulation
approximately 400 nm to the northwest were inducing the poleward motion.
(A second TCFA was issued for the second disturbance at 1300 UTC.)
At 04/0000 UTC JTWC upped the MSW (1-min avg) to 50 kts while MFR
upgraded Tropical Disturbance 16 to depression status (30 kts 10-min
avg). The system was then located approximately 360 nm northeast of
Mauritius and moving southwestward at 15 kts. The second circulation
was located about 350 nm to the north-northwest of TC-28S. The system
was forecast to gradually assume a westerly track as a mid-level trough
to the south and a low to mid-level ridge to the southwest translated
eastward.
B. Storm History
----------------
Mauritius upgraded the system to Tropical Storm Manou at 04/0600 UTC.
MFR estimated the MSW (10-min avg) at 35 kts and Manou remained a minimal
35-kt tropical storm (per MFR's warnings) for a full three days. JTWC
reduced the 1-min avg MSW to 45 kts at 1200 UTC and their intensity
estimates fluctuated between 35 and 45 kts for the next few days. At
1200 UTC on 4 May Manou's center was located approximately 300 nm north-
east of Mauritius. The vertical shear appeared to have lessened with
multi-spectral imagery revealing a partially-exposed LLCC to the north-
east of the deep convection. The second circulation to the west showed
signs of weakening as it drew close to Manou, and JTWC cancelled the
TCFA for that system at 1300 UTC.
Tropical Storm Manou moved steadily in a general west-southwesterly
direction during the 5th, influenced by the low to mid-level ridge to
the southwest. The system appeared to weaken some as microwave imagery
around 1200 UTC revealed a fully-exposed LLCC northeast of the deep
convection. Manou was located about 190 nm north of Mauritius at
0000 UTC on 6 May, moving southwestward at 7 kts. The southwesterly
motion was attributed to the influence of a passing trough to the south.
Animated infrared imagery suggested that the LLCC had moved closer to
the convection. By 1800 UTC the tropical storm was located northwest
of Mauritius and had resumed a west-southwesterly track at 9 kts. A
synoptic report of 40-kts prompted JTWC to up the intensity to 40 kts
from 35 kts on the previous warning. Deep convection had re-organized
over the center after weakening earlier in the day.
By 0600 UTC on 7 May Tropical Storm Manou was located about 250 nm
northwest of Reunion Island, and had continued to strengthen. MFR raised
the intensity to 40 kts, and JTWC upped the 1-min avg MSW estimate to
45 kts. Manou continued trekking to the west-southwest as it slowly
intensified. At 1800 UTC MFR and JTWC increased the MSW to 45 and
55 kts, respectively. By 08/0600 UTC visible imagery indicated the
formation of a small banding eye. MFR upgraded Manou to tropical
cyclone (i.e., hurricane) status with the MSW estimated at 70 kts (10-min
avg). The cyclone's center at that time was only 40 nm off the east
coast of Madagascar, moving west-southwestward at 8 kts.
Tropical Cyclone Manou came to a screeching halt at it neared the
coast of Madagascar. By 1200 UTC on 8 May the cyclone had reached its
peak intensity of 80 kts (10-min avg) with an estimated CP of 952 mb.
Gales reached out 80-100 nm around the 24-nm diameter eye--the radius
of 50-kt winds was estimated at 35 nm. (Interestingly, JTWC's peak 1-min
avg MSW for Manou was lower than MFR's peak 10-min avg intensity. The
peak MSW per JTWC's warnings was 75 kts. However, the CI estimates
referenced in the JTWC warnings ranged from 75 to 90 kts. The JTWC
forecasters in this case chose to follow the lower Dvorak estimates while
MFR went with the higher ones.) The eye of Manou was centered only
10 nm off the coast of Madagascar at 1800 UTC, practically stationary.
The storm moved very little for the next 12-18 hours, then gradually
began to inch southward on the 9th along the western periphery of a
mid-level ridge to the east.
The eye continued to straddle the coast as Manou drifted southward.
The cyclone began to weaken on the 9th due to land interaction and dry
air entrainment. MFR downgraded Manou to a 60-kt tropical storm at
09/1200 UTC, and JTWC lowered the 1-min avg MSW to 55 kts in their next
warning at 1800 UTC. The system continued to move slowly southward just
off the east coast of Madagascar through the remainder of the 9th and
on the 10th with MFR downgrading it to tropical depression status at
0600 UTC. By 1800 UTC on 10 May Manou had lost almost all of its deep
convection and the LLCC was difficult to locate. Both MFR and JTWC
issued their final warnings on Manou at this time with the dissipating
center located about 40 nm east of the coast of Madagascar.
C. Meteorological Observations
------------------------------
I have a few surface observations sent by Karl Hoarau and Patrick
Hoareau--a special thanks to these guys for sending along the infor-
mation. St. Brandon Island (WMO 61986; 16.5S, 59.6E; 4 m elevation)
experienced winds gusting above gale force for an extended period as
Tropical Storm Manou moved slowly by to the north. Peak gusts reached
or exceeded 34 kts from 04/0000 UTC through at least 05/1800 UTC (the
record ends at that time). The hourly observation with the strongest
sustained wind and peak gust was at 04/1400 UTC. The station reported
a 10-min avg wind of 40 kts with a maximum gust of 59 kts--the SLP at
that time was 998.3 mb. Manou was then centered approximately 60 nm
north-northeast of the island. The minimum SLP of 995.0 nm was measured
at 05/0000 UTC when the storm's center was about 50 nm north-northwest
of St. Brandon.
Mauritius also experienced some rather strong gusts from Tropical
Storm Manou. Following are listed several reporting stations in
Mauritius with the peak gusts experienced during Manou's approach:
Le Domaine des Pailles - 58 kts
Le Morne - 55 kts
Trou aux Cerfs - 49 kts
Fort William - 45 kts
Nouvelle-Decouverte - 43 kts
Bain-Bouf - 43 kts
Queen-Victoria - 41 kts
Port-Louis - 40 kts
Souillac - 39 kts
At Vatomandry, Madagascar, a city which was severely damaged by the
cyclone, reports indicate that a peak gust of 114 kts was recorded. The
same location recorded 227 mm of rain between midnight and 1500 local
time on 9 May.
The appearance of Manou in satellite imagery, the magnitude of the
winds reported in coastal Madagascar, and the level of damage caused
by the cyclone (see Section D) all suggest that Manou was a strong
Category 2 or possibly Category 3 cyclone on the Saffir/Simpson Scale
at the time of its closest approach to Madagascar.
D. Damage and Casualties
------------------------
Tropical Cyclone Manou struck a destructive blow to Madagascar.
Reports indicate that the city of Vatomandry was almost 90% destroyed.
Electricity, telecommunications and water networks were badly damaged,
and roads and bridges were destroyed. In Vatomandry around 24,500
homes were destroyed and 47,500 persons left homeless. In Brickaville
and Andevoranto, 95% of dwellings were destroyed. Agricultural losses
were also high: 80% of the rice crop in the region was destroyed and
the corn crop was also severely damaged. The final death toll was
placed at 70 with 19 still missing a few weeks after the storm. Also,
about 85 persons were reported as suffering injuries related to the
cyclone. Over 115,000 persons in and around Vatomandry were adversely
affected by Manou.
Additional articles concerning the effects of Tropical Cyclone Manou
can be found at the following website:
http://www.reliefweb.int/w/rwb.nsf/vLND>
E. A Little Climatology
-----------------------
Karl Hoarau looked up some statistics on May tropical cyclones in
the Southwest Indian Ocean and sent them to me. A thanks to Karl for
sharing this information.
A May tropical cyclone (hurricane) is not a really rare event in the
Southwest Indian Ocean, but they do not occur all that frequently either.
Since the beginning of the satellite era, four tropical cyclones of at
least 75 kts have formed in the basin:
Kesiny, 75 kts on 9 May 2002 at 0900 UTC - 1200 UTC near 10.5S/50.5E
Konita, 90 kts on 5 May 1993 at 0000 UTC near 10.5S/68.5E
Ikonjo, 75 kts on 18 May 1990 at 0600 UTC near 7.5S/53.7E
Lila, 90 kts on 10 May 1986 at 1200 UTC near 16.7S/89.7E
Tropical Cyclone Manou is the fifth, and it is the most remarkable
one because it is the first time that a tropical cyclone has reached a
significant intensity near 19S-20S in May. A very strong vertical wind
shear is a usual climatological feature in May in the Southwest Indian,
especially near 20S.
One last bit of information: only one tropical cyclone is estimated
to have reached 100 kts in May in the South Indian Ocean. That one was
Tropical Cyclone Rhonda on 14 May 1997 from 0000 UTC to 1200 UTC at the
intensiy of 100 kts near 16S/97E (in the AOR of the Perth TCWC).
(Report written by Gary Padgett with a contribution by Karl Hoarau)
*************************************************************************
NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E
Activity for May: 1 tropical LOW
Northwest Australia/Southeast Indian Ocean
Tropical Activity for May
------------------------------------------
No tropical cyclones formed in waters between 90E and 135E during
May. A weak tropical LOW had formed by 8 May about 375 nm northwest of
the Cocos Islands. This system was a Southern Hemisphere twin to the
more intense Tropical Cyclone 01B in the Bay of Bengal. The LOW drifted
east-southeastward, passing just north of the Cocos on the 10th, and was
last mentioned in Perth's daily Tropical Weather Outlooks on the 11th
when it was located approximately 150 nm east of the islands. No gale
warnings were issued, and the potential for tropical cyclone development
was rated low each day. Maximum winds likely did not exceed 20-25 kts.
*************************************************************************
NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E
Activity for May: No tropical cyclones
*************************************************************************
SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E
Activity for May: No tropical cyclones
*************************************************************************
EXTRA FEATURE
In order to shorten the amount of typing in preparing the narrative
material, I have been in the habit of freely using abbreviations and
acronyms. I have tried to define most of these with the first usage
in a given summary, but I may have missed one now and then. Most of
these are probably understood by a majority of readers but perhaps a
few aren't clear to some. To remedy this I developed a Glossary of
Abbreviations and Acronyms which I first included in the July, 1998
summary. I don't normally include the Glossary in most months in
order to help keep them from being too long. If anyone would like to
receive a copy of the Glossary, please e-mail me and I'll be happy
to send them a copy.
*************************************************************************
AUTHOR'S NOTE: This summary should be considered a very preliminary
overview of the tropical cyclones that occur in each month. The cyclone
tracks (provided separately) will generally be based upon operational
warnings issued by the various tropical cyclone warning centers. The
information contained therein may differ somewhat from the tracking and
intensity information obtained from a "best-track" file which is based
on a detailed post-seasonal analysis of all available data. Information
on where to find official "best-track" files from the various warning
centers will be passed along from time to time.
The track files are not being sent via e-mail. They can be retrieved
from the archive sites listed below. (Note: I do have a limited e-mail
distribution list for the track files. If anyone wishes to receive
these via e-mail, please send me a message.)
Both the summaries and the track files are standard text files
created in DOS editor. Download to disk and use a viewer such as
Notepad or DOS editor to view the files.
The first summary in this series covered the month of October,
1997. Back issues can be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Michael Pitt, and
Chris Landsea):
http://australiasevereweather.com/cyclones/>
http://www.typhoon2000.ph> OR http://64.235.42.210>
http://mpittweather.com>
ftp://ftp.aoml.noaa.gov/hrd/pub/landsea/padgett/>
Another website where much information about tropical cyclones may
be found is the website for the UK Meteorological Office. Their site
contains a lot of statistical information about tropical cyclones
globally on a monthly basis. The URL is:
http://www.met-office.gov.uk/sec2/sec2cyclone/sec2cyclone.html>
TROPICAL CYCLONE REPORTS AVAILABLE
JTWC now has available on its website the complete Annual Tropical
Cyclone Report (ATCR) for 2001 (2000-2001 season for the Southern
Hemisphere). ATCRs for earlier years are available also. Recently
added was the report for the Southern Hemisphere 2001-2002 season.
The URL is: http://199.10.200.33/jtwc.html>
Also, TPC/NHC has available on its webpage nice "technicolor"
tracking charts for the 2002 Atlantic and Eastern North Pacific
tropical cyclones; also, preliminary storm reports for all the 2002
Atlantic and Eastern North Pacific cyclones are now available, as
well as track charts and reports on storms from earlier years.
The URL is: http://www.nhc.noaa.gov>
A special thanks to Michael Bath of McLeans Ridges, New South Wales,
Australia, for assisting me with proofreading the summaries.
PREPARED BY
Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327
John Wallace (Eastern North Pacific, North Indian Ocean, Western
Gulf of Mexico)
E-mail: [email protected]
Kevin Boyle (Eastern Atlantic, Western Northwest Pacific, South
China Sea)
E-mail: [email protected]
Simon Clarke (Northeast Australia/Coral Sea, South Pacific)
E-mail: [email protected]
*************************************************************************
*************************************************************************